In other words, the axioms of geometry (I do not speak of those of arithmetic) are merely disguised definitions. - Henri Poincaré

One need only open the eyes to see that the conquests of industry which have enriched so many practical men would never have seen the light, if these practical men alone had existed and if they had not been preceded by unselfish devotees who died poor, who never thought of utility, and yet had a guide far other than caprice.
As Mach says, these devotees have spared their successors the trouble of thinking.

We have selected the most convenient space, but experience has guided our choice; as this choice has been unconscious, we think it has been imposed upon us […] In this progressive education whose outcome has been the construction of space, it is very difcult to determine what is the terms of use, part of the individual, what the part of the race. How far could one of us, transported from birth to an entirely diferent world, where were dominant, for instance, bodies moving in conformity to the laws of motion of non-Euclidean solids, renounce the ancestral space to build a space completely new?

only the relations between things. Outside of these relations there is no knowable reality.